The island of Madeira, of volcanic origin, was discovered in 1419 by the Portuguese Captain, Joao Goncalves Zarco, and is an archipelago composed of two inhabited islands Madeira and Porto Santo and two small uninhabited islets, the Desertas and the Selvagens. Madeira's location in the Atlantic made it an important strategic port of call which led to the rapid expansion of the island's wine, especially in countries such as the United States of America. It was so popular in the USA that in the 18th century, Madeira wine is reported to have represented over 75% of all wine imported into this market.